I've built a few things usually spending a good amount of time dealing with miscellaneous problems that pop up in the SL end of the pipeline but these problems have given me a little knowledge on how to work around them and what to recommend to others who may suffer the same fate!
1 Symmetry
Well basic texturing options give you the option of flipping an image or rotating it, the sculpty is a bit more complex and this function will produce problems as I'm sure you've noticed if you’re reading this. I'm sure it will be implemented eventually but there is a work around already practiced in SL.
Instead of 2 symmetrical shapes sharing the same geometry mirrored over an axis try creating identical objects which can take advantage of mirrored textures. Its cheaper to upload one sculpt map than two. Plus it’s more efficient if you make them use the same texture.
If you insist on creating unique symmetrical shapes the simplest way is to mirror it first and preview it before you pay to upload it. You will notice problems in the preview before you commit it to your inventory. Usually the problems are as simple as flipping the UVs or surface normals. Where normals aren't calculated (I believe) I have noticed that from time to time that’s the only problem with a model.
2 Complexity
You all will notice really fast that Sculpties is not the cure-all solution for problems you'll encounter with the normal building method in SL, in fact it’s just the opposite. If you try to make something massively complicated in ONE sculpty you'll notice it will be a geometric mess due to the restrictions placed on this feature. at most any given object will have a max of 1024 polygons (quad faces, 2048 tris) on the object at the most detailed level of detail (LOD 0)
This isn’t to say you should dismiss sculpties as a useless feature. It’s simply meant to supplement the existing tools. The workflow you should practice in building is to break up your objects into smaller pieces. If you don’t you'll end up with two possible outcomes. 1- A jagged UN-detailed mesh full of jagged and misplaced edges and completely incorrect angles or 2- just a tangled mesh of its former glory.
The key to understanding sculpties is how geometry is distributed. Since a sculpty is generated from a Sculpt Map; a texture file. It relies heavily on the texture information created from UVs. sculpties do conform to UVs technically but more accurately the object your building conforms to the UVs of the Sculpty. If you make a Poly plane you'll notice that the UVs are evenly spaced. At 1024 polys the geometry is more compact. Even a relatively simple tube can become a jagged mess when you don’t consider this way of thinking.
If you can swing it try to create a plane with 1024 polys and apply that UV spacing to your model, it will save you some problems.
3 Texturing
As I mentioned before a sculpty relies heavily on the texture end of building. However as a model you generate the normal methods of texturing in SL don’t completely apply since the UVs of the original model can be manipulated. (again your minipulating the displacement of geometry more than the actual UV information) Things can get hairy really fast if you decide to use default textures. The same can be said if you decide to paint your textures by hand in programs like Photoshop Paintshop or Gimp. The UVs of a sculpty can be a bit daunting to attack with the airbrush tool.
It’s been said before that the ability to Project textures and baking should be taken advantage of. Just because this model is going into SecondLife doesn’t mean you can’t take advantage of the more advanced features of your 3d Package either. The use of Mental Ray or VRay can be used to create detailed textures which can be baked down and composited together.
Just because it’s a texture map doesn’t mean it has to be painted, movie and game professionals have used various compositing methods to produce extremely realistic results on games and movies which may have had worse or less visual effects than SL. if you're in doubt try to find a tutorial. it doesn’t have to be for Second Life proper so long as it is for the part of the project your looking for (IE modeling, texturing, projection, texture compositing ect ect ect) if you know what your doing you can adapt these tutorials towards the end result of your project.
4 Assembly
Well you've seen that your models look fine in the previewer and you've uploaded them to SL. Now you face a few new problems. weather your assembling a prop or placing a simple attachment you've noticed that Sculpties are a bit random when it comes to their size as of yet there is no unified import scale so some small pieces may be huge or some large pieces may be smaller than they are supposed to be.
As near as I can tell this is because when the objects are sampled, it’s done locally and in relation to that objects relation to its origin and bounding box. So this can throw off the balance of a model when things don’t match up or are off center ect ect.
I find that it’s usually easier to assemble something if you have something to go by. If you use projection textures on your model you'll notice where one object ends and the next begins though it gets inaccurate when the scale is messed up. You may suffer some Asymmetrical objects on objects that are inline such as weapons like swords or rifles/pistols or guns in general. Remember than its sampled from the center out. [to my knowledge, there are some discussions elsewhere in the SL forums where they are trying ring objects like inner-tubes and such, needless to say in that instance its a different principal] if a piece isn’t symmetrical and you center it [by making all objects have the same translation value over one axis] its going to stick out.
As a sub note to Assembly,
I've also recently discovered that you can have an open ended sculpty if it’s assembled correctly.
there are several methods of modeling where you create segments or "patches" of a larger object to either concentrate on detail or break up sections to achieve better results (similar to how the SL Avatar geometry is divided into several groups/sets to accommodate textures and deformations) like lip-syncing or dynamic geometry.
Or a method of modeling where only half of a symmetrical object is created (like a head) and the results are mirrored and connected. This method can be used when working with sculpties to accommodate more geometry that might have otherwise been lost to interpenetration (geometry clipping into other geometry) instead of connecting the mirrored geometry you can simply export it as a unique, all be it mirrored, object.
This method can also be used to squeeze a few more faces into objects which are otherwise too complicated to export under the geometry restrictions of the Sculpt map.
This method has its own drawbacks though. Unless geometry is perfectly aligned you'll get really bad seems. If there are any gaps and open edges you'll see straight threw your model since SL renders its geometry as one-sided objects.
This method shouldn’t be used as a hack. If you’re attempting to circumvent the detail restrictions of sculpties just for quality your missing the point of creating your own content and messing with the stability of the engine which isn’t designed for a half million faces of geometry on/near a single avatar. Not to mention how ghastly expensive it would be to upload a demonstrable complicated patch modeled piece of geometry (and textures!). I'm sure that any attempts to use this as a grifing tactic will get the offenders banned.
I hope that this document helps people make more interesting stuff for second life. I hate to hold on to information which might help others so here you go!